The present invention relates to a method and a device for forming plastic preforms into plastic containers. Such methods and devices have been known for some time from the prior art. Normally, heated plastic preforms are formed into plastic containers by pressurizing with compressed air. In the prior art, usually several pressure stages are used to expand the plastic preforms. It is known firstly to carry out a pre-inflation with a low pressure and then finally inflate the plastic preforms with a higher pressure. In addition, in the prior art normally an intermediate inflation is applied, which temporally lies between the pre-inflation and the final inflation. This plurality of different pressure stages leads to a comparatively great complexity of reservoirs which are normally configured as ring channels. Also, the actual procedure for forming the plastic preforms is relatively complex. On the other hand, previously it was assumed that in particular the provision of an intermediate blowing pressure level greatly simplifies or improves the blow moulding process.